1. Field of the Invention
This invention relates generally to instrument seals in surgical devices and most specifically to septum seals in laparoscopic trocars.
2. Discussion of Related Art
Less invasive abdominal surgery, commonly referred to as laparoscopic surgery, is undertaken with instruments extending across the abdominal wall. In this procedure, the volume of the abdominal surgical site is increased by inflating the abdomen with a gas. In order to maintain the pressure of the gas within the abdomen while passing instruments across the abdominal wall, access devices, commonly referred to as trocars, are positioned through holes in the abdomen. These trocars are provided with seals which engage the instruments as they are passed through the trocar and into the inflated abdomen.
The seals most commonly used for this purpose are septum seals which are elastomeric and are generally planar in configuration. The septum seals are generally made of a thin material that may tend to engage the body or shaft of an inserted instrument and be drawn along with the axial motion of the instrument as the instrument is placed, used, or removed through the septum seals. These seals extend across a working channel of the trocar and form a seal with the instrument as the instrument is passed through a hole in the septum seal. When the instrument is inserted, the septum seal is pushed generally in the distal direction as it forms a seal with the instrument. When the instrument is withdrawn, the opposite effect occurs; the septum seal is pulled generally in the proximal direction causing the seal to invert. This inversion can add undesirable friction during use of the instrument and may cause the septum to bind or gather between the instrument and portions of the seal housing or floating ring or other adjacent structures when the instrument is withdrawn.